Hello together,
we get the same error. Environment ist vCenter 6.5 U1 (Hosts are 6.0). In a previous version of OpenNebula (eg 5.2.0) importing templates ist still working fine.
I followed the advise in the following thread: Error : Import Template Vcenter (Opennebula 5.4)
If you see tinovas post (a bit further down), but replacing the virtual_machine.rb file does not work. You run into another error message. Sorry dont have the message anymore.
Seems to be a problem with the vCenter driver (maybe :)).
Greetings
Pascal